Mobile wireless communication devices such as cellular telephones, smartphones, personal digital assistants (PDAs). etc. can be configured to communicate with other devices over a multitude of different frequencies. As such, mobile wireless communication devices are required to include communication receivers capable of receiving communication signals at a multitude of different frequencies. In some situations, it is desirable to receive and demodulate two or more communication signals in different frequency bands using a technique referred to as multi-carrier aggregation. In this way, a larger bandwidth is available so that more information can be transmitted per second to provide a more pleasing user experience.
To this end, conventional communication receivers often include mixers for performing a frequency up-conversion or a frequency down-conversion of the received communication signals using a sinusoidal mixing signal with a desired frequency. Conventionally, such mixers include a phase locked loop (PLL) for every frequency band, which, however, drastically increases area and power consumption of the communication receiver. A similar problem arises in frequency-division duplexing (FDD), where a mobile wireless communication device receives and transmits at the same time, but at different frequencies such that at last two PLLs are necessary.
Thus, there is a need for an improved communication apparatus and method, in particular an improved communication receiver or communication transmitter and communication method suitable for multi-carrier aggregation.